EVC Quality of Service

This document contains information about how to enable quality of service (QoS) features (such as traffic classification and traffic policing) for use on an Ethernet virtual circuit (EVC).

An EVC as defined by the Metro Ethernet Forum is a port-level point-to-point or multipoint-to-multipoint circuit. It is an end-to-end representation of a single instance of a service being offered by a provider to a customer. It embodies the different parameters on which the service is being offered.

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release notes for your platform and software release. To find information about
the features documented in this module, and to see a list of the releases in
which each feature is supported, see the feature information table.

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Information About Quality of Service on an EVC

EVC Quality of Service and the MQC

QoS functionality is typically applied using traffic classes, class maps, and policy maps. For example, you can specify that traffic belonging to a particular class be grouped into specific categories, and receive a specific QoS treatment (such as classification or policing). The QoS treatment the traffic is to receive is specified in a policy map and the policy map is attached to an interface. The mechanism used for applying QoS in this manner is the modular QoS CLI (MQC.)

The policy map can be attached to an interface in either the incoming (ingress) or outgoing (egress) direction with the
service-policy command.

The MQC structure allows you to define a traffic class, create a traffic policy, and attach the traffic policy to an interface (in this case, an EVC).

The MQC structure consists of the following three high-level steps.

Define a traffic class by using the
class-mapcommand. A traffic class is used to classify traffic.

Create a traffic policy by using the
policy-map command. (The terms
trafficpolicy and
policymap are often synonymous.) A traffic policy (policy map) contains a traffic class and one or more QoS features that will be applied to the traffic class. The QoS features in the traffic policy determine how to treat the classified traffic.

Attach the traffic policy (policy map) to the interface by using the
service-policy command.

Note

For more information about the MQC, including information about hierarchical policy maps and class maps, see the "Applying QoS Features Using the MQC" module.

QoS-Aware Ethernet Flow Point (EFP)

As described in the EVC Quality of Service and the MQC, the MQC is used to apply one or more QoS features to network traffic. The last step in using the MQC is to attach the traffic policy (policy map) to an interface (in this case, an EVC) by using the service-policy command.

With the EVC Quality of Service feature, the service-policy command can be used to attach the policy map to an Ethernet Flow Point (EFP) in either the incoming (ingress) or outgoing (egress) direction of an EVC. This way, the EFP is considered to be "QoS-aware."

QoS Functionality and
EVCs

The specific QoS
functionality includes the following:

Packet
classification (for example, based on differentiated services code point (DSCP)
value and QoS group identifier)

Packet marking
(for example, based on Class of Service (CoS) value)

Traffic policing
(two- and three-color and multiple actions)

Bandwidth sharing

Priority queueing
(in the outbound direction on the EVC only)

Weighted Random
Early Detection (WRED)

The QoS functionality
is enabled by using the appropriate commands listed in the following sections.

match Commands Supported by EVC QoS for Classifying Traffic

The table below lists
some of the available
match commands that can be used when classifying traffic on an EVC. The available
match commands vary by Cisco IOS XE release. For more information about the commands and command syntax, see the Cisco IOS Quality of Service Solutions Command Reference.

Table 1 match Commands That Can Be Used with the MQC

Command

Purpose

matchaccess-group

Configures the match criteria for a class map on the basis of the specified access control list (ACL).

matchany

Configures the match criteria for all packets.

matchcos

Matches a packet based on a Layer 2 CoS marking.

matchcosinner

Matches the inner CoS of QinQ packets on a Layer 2 CoS marking.

match [ip]
dscp

Identifies a specific IP DSCP value as a match criterion. Up to eight DSCP values can be included in one match statement.

matchnot

Specifies the single match criterion value to use as an unsuccessful match criterion.

Note

The
matchnot command, rather than identifying the specific match parameter to use as a match criterion, is used to specify a match criterion that prevents a packet from being classified as a member of the class. For instance, if the
matchnotqos-group6command is issued while you configure the traffic class, QoS group 6 becomes the only QoS group value that is not considered a successful match criterion. All other QoS group values would be successful match criteria.

match [ip]
precedence

Identifies IP precedence values as match criteria.

matchqos-group

Identifies a specific QoS group value as a match criterion.

matchsource-addressmac

Uses the source MAC address as a match criterion.

Note

Classifying traffic using the
matchsource-addressmaccommand is supported in the input direction only.

matchvlan(QoS)

Matches and classifies traffic on the basis of the VLAN identification number.

match vlan inner

Configures a class map to match the innermost VLAN ID in an 802.1q tagged frame.

Multiple match Commands in One Traffic Class

If the traffic class contains more than one match command, you need to specify how to evaluate the match commands. You specify this by using either the match-any or match-allkeyword of the class-map command. Note the following points about the match-any and match-all keywords:

If you specify the match-anykeyword, the traffic being evaluated by the traffic class must match one of the specified criteria.

If you specify the match-all keyword, the traffic being evaluated by the traffic class must match all of the specified criteria.

If you do not specify either keyword, the traffic being evaluated by the traffic class must match all of the specified criteria (that is, the behavior of the match-all keyword is used).

Commands Used to Enable QoS
Features on the EVC

The commands used to
enable QoS features vary by Cisco IOS XE release. The table below lists
some of the
available commands and the QoS features that they enable. For complete command
syntax, see the Cisco IOS Quality of Service Solutions Command Reference.

For more information
about a specific QoS feature that you want to enable, see the appropriate
module of the Cisco IOS Quality of Service Solutions Configuration Guide.

Specifies or
modifies the maximum number of packets the queue can hold for a class
configured in a policy map.

random-detect

Enables
Weighted Random Early Detection (WRED).

random-detect cos-based

Enables Weighted random early detection (WRED) on the basis of
the class of service (CoS) value of a packet.

random-detect dscp-based

Specifies that Weighted random early detection (WRED) is to use
the differentiated services code point (DSCP) value when it calculates the drop
probability for a packet.

random-detectdiscard-class

Configures
the WRED parameters for a discard-class value for a class in a policy map.

random-detectdiscard-class-based

Configures
WRED on the basis of the discard class value of a packet.

random-detectexponential-weighting-constant

Configures
the exponential weight factor for the average queue size calculation for the
queue reserved for a class.

random-detectprecedence

Configure
the WRED parameters for a particular IP Precedence for a class policy in a
policy map.

service-policy

Specifies
the name of a traffic policy used as a matching criterion (for nesting traffic
policies [hierarchical traffic policies] within one another).

setcos

Sets the
Layer 2 CoS value of an outgoing packet.

setcos-inner

Marks the inner class of service field in a bridged frame.

setdiscard-class

Marks a
packet with a discard-class value.

set[ip]
dscp

Marks a
packet by setting the DSCP value in the type of service (ToS) byte.

setmplsexperimental

Designates
the value to which the Multiprotocol Label Switching (MPLS) bits are set if the
packets match the specified policy map.

setprecedence

Sets the
precedence value in the packet header.

setqos-group

Sets a QoS
group identifier (ID) that can be used later to classify packets.

shape

Shapes
traffic to the indicated bit rate according to the algorithm specified.

input and output Keywords of
the service-policy Command

As a general rule,
the QoS features configured in the traffic policy can be applied to packets
entering the interface or to packets leaving the interface. Therefore, when you
use the
service-policy
command, you need to specify the direction of the traffic policy by using the
input or
output keyword.

For instance, the
service-policyoutputpolicy-map1 command would apply the QoS features
in the traffic policy to the interface in the output direction. All packets
leaving the interface (output) are evaluated according to the criteria
specified in the traffic policy named policy-map1.

Note

For Cisco releases, queueing mechanisms are not supported in the input
direction. Nonqueueing mechanisms (such as traffic policing and traffic
marking) are supported in the input direction. Also, classifying traffic on the
basis of the source MAC address (using the
matchsource-addressmac command) is supported in the input direction
only.

How to Configure a Quality of Service Feature on an EVC

Creating a Traffic Class for Use on the EVC

To create a traffic class, use the class-map command to specify the traffic class name. Then use one or more match commands to specify the appropriate match criteria. Packets matching the criteria that you specify are placed in the traffic class.

To create the traffic class for use on the EVC, complete the following steps.

SUMMARY STEPS

1.enable

2.configureterminal

3.class-map [match-all | match-any] class-name

4.matchcoscos-number

5.
Enter additional match commands, if applicable; otherwise, proceed with the next step.

6.end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

Enter your password if prompted.

Step 2

configureterminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

class-map [match-all | match-any] class-name

Example:

Router(config)# class-map match-any class1

Creates a class map and enters class-map configuration mode.

The class map is used for matching packets to the specified class.

Note

The match-all keyword specifies that all match criteria must be met. The match-any keyword specifies that one of the match criteria must be met. Use these keywords only if you will be specifying more than one match command.

Step 4

matchcoscos-number

Example:

Router(config-cmap)# match cos 2

Matches a packet on the basis of a Layer 2 CoS number.

Note

The matchcos command is an example of a match command you can use.

Step 5

Enter additional match commands, if applicable; otherwise, proceed with the next step.

Configuring the EVC and Attaching a Traffic Policy to the EVC

The traffic policy (policy map) applies the enabled QoS feature to the traffic class once you attach the policy map to the EVC.

To configure the EVC and attach a traffic policy to the EVC, complete the following steps.

Note

One of the commands used to attach the traffic policy to the EVC is the service-policy command. When you use this command, you must specify either the input or output keyword along with the policy map name. The policy map contains the QoS feature you want to use. Certain QoS features can only be used in either the input or output direction. For more information about these keywords and the QoS features supported, see the input and output Keywords of the service-policy Command.
Also, if you attach a traffic policy to an interface containing multiple EVCs, the traffic policy will be attached to all of the EVCs on the interface.

RFCs

RFC

Title

No new or modified RFCs are supported, and support for existing RFCs has not been modified.

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Feature Information for
Configuring EVC Quality of Service

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Table 3 Feature Information for EVC
Quality of Service

Feature
Name

Releases

Feature
Information

EVC Quality
of Service

Cisco IOS
XE Release 3.3

Cisco IOS Release 15.5(2)T

This
document contains information about how to enable quality of service (QoS)
features (such as traffic classification and traffic policing) for use on an
Ethernet virtual circuit (EVC).

The EVC
Quality of Service feature was introduced on the Cisco ASR 1000 Series
Aggregation Services Router.

The
following commands were introduced or modified:
service-policy,
showpolicy-mapinterfaceserviceinstance.